Arp with Alternate Higher Pitched Note by Florentino
Feed a constant notes to the synth and it will generate a higher pitch note on every alternate pulse, the speed of the arp is controlled by the rate of the LFO.
Play with the Att2 for some pulse width modulation.
Play with the Delay mix knob to get interesting harmonics.
You can add randomness if you want by using the S&H.